Verifying Greenhouse Gas Emissions: Methods to Support International Climate Agreements

1. Verifying Greenhouse Gas Emissions: Methods to Support International ClimateAgreements Stephen Pacala March 16, 2010

2. Committee Members Stephen Pacala, (Chair), Princeton University Clare Breidenich, Independent Consultant Peter Brewer, Monterey Bay Aquarium Research Institute Inez Fung, University Of California, Berkeley Michael Gunson, Jet Propulsion Laboratory Gemma Heddle, Chevron Corporation Beverly Law, Oregon State University Gregg Marland, Oak Ridge National Laboratory Keith Paustian, Colorado State University Michael Prather, University of California, Irvine James Randerson, University of California, Irvine Pieter Tans, National Oceanic and Atmospheric Administration Steven Wofsy, Harvard University NRC Staff: Anne Linn

3. Context for the Study • Anthropogenic greenhouse gases are accumulating in the atmosphere • International agreements to limit future greenhouse gas emissions will rest on the ability of each country to estimate emissions accurately and to monitor and verify changes over time Scripps CO2 program

4. Committee Charge and Focus Charge: Review current methods and propose improved methods for estimating and verifying greenhouse gas emissions at different spatial (e.g., national, regional, global) and temporal (e.g., annual, decadal) scales. The committee focused on the gases, methods, and scales relevant to international climate agreements • National, annual emissions and decadal trends • Public domain information

5. Greenhouse Gases Covered • Carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), sulfur hexafluoride (SF6), chlorofluorocarbons (CFCs), hydrofluorocarbons (HFCs), and perfluorinated hydrocarbons (PFCs) • result from human activities • long lifetimes in the atmosphere • currently included in international agreements • Particular focus on CO2 • largest single contributor to global climate change

6. Bottom Line • National fossil-fuel CO2 emissions can be estimated by each nation accurately enough to support a climate treaty (error <10%). • Strategic investments could enable accurate independent checks on self-reported estimates of CO2 emissions from fossil fuel and deforestation within 5 years (<10% for critical countries) • Estimates of emissions of other greenhouse gases will remain uncertain in the near term IPCC (2007)

7. One-quarter of countries are responsible for 80% of global emissions

8. Methods for Estimating Emissions UNFCCC National inventories Estimates anthropogenic emissions and removals (sinks) Based on measurements of human activities Tracer-transport inversion Estimates net anthropogenic and natural sources and sinks Based on atmospheric and/or oceanic measurements of the gases and models of air and water flow Land-use measurements and models Estimates emissions and sinks of CO2, CH4, and N2O Based on land cover information from satellite imagery and biogeochemical models

9. UNFCCC Inventory Emission = Activity Level X Emissions Factor (i.e. steel prod.) X (CO2 per unit prod.) Current error: <10% for CO2 from developed countries but up to 50% for CH4 and 100% or more for N2O, CFC’s, PFC’s, HFC’s and SF6.

10. Methods for Estimating Emissions UNFCCC National inventories Estimates anthropogenic emissions and removals (sinks) Based on measurements of human activities Tracer-transport inversion Estimates net anthropogenic and natural sources and sinks Based on atmospheric and/or oceanic measurementsof the gases and models of air and water flow Land-use measurements and models Estimates emissions and sinks of CO2, CH4, and N2O Based on land cover information from satellite imagery and biogeochemical models

11. Tracer-Transport Inversion Current errors of 100% or more for all gases. CO2 Prevailing Wind CO2 Sampler LAND Fossil-fuel CO2 Emissions CO2 Sampler

12. Problems with Tracer Transport Method • Transport Error • Large and incompletely understood background fluctuations of natural emissions. • Current sampling grid avoids urban areas and large industrial sources which generate most emissions. • Current sampling grid is too sparse.

13. Atmospheric Sampling Network

14. Methods for Estimating Emissions UNFCCC National inventories Estimates anthropogenic emissions and removals (sinks) Based on measurements of human activities Tracer-transport inversion Estimates net anthropogenic and natural sources and sinks Based on atmospheric and/or oceanic measurements of the gases and models of air and water flow Land-use measurements and models Estimates emissions and sinks of CO2, CH4, and N2O Based on land cover information from satellite imagery and biogeochemical models

15. Methods for Estimating Emissions Errors up to 100% or more for all gases. Models convert changes visible in the imagery into carbon emissions

16. Categories of Recommendations • Strengthening national greenhouse gas inventories • Improving independent estimates of fossil-fuel CO2 emissions • Improving independent estimates of fluxes from land-use sources and sinks

17. Developed countries Produce annual estimates of sources and sinks of 6 greenhouse gases Use the most rigorous methods → most accurate UNFCCC review of methods and data sources Developing countries Make periodic estimates of CO2, CH4, and N2O (many countries have produced only 1 inventory) Use simplest methods → least accurate No UNFCCC review Current Differences in Estimating and Reporting Emissions

18. Recommendation UNFCCC parties should strengthen self-reported national emissions inventories by working toward • Extending regular, rigorous reporting and review to developing countries • Extending top-tier (most stringent) IPCC methods to the most important greenhouse gas sources in each country This would reduce errors to <10% for CO2, and, depending on the country, from <10% to 50% for CH4, from 10% to 100% for N2O, and from <10% to 50% for the fluorinated gases. Financial and technical assistance will be required to help developing countries collect, analyze, and report emissions regularly.

19. Recommendation Annex I (developed) countries should develop and implement standardized methods for preparing and publishing inventories that are gridded at spatial and temporal resolutions appropriate for the particular greenhouse gas and source • UNFCCC inventories report annual, national totals, even when more detailed information is collected • Gridded inventories would facilitate independent checks using atmospheric data and models

20. Categories of Recommendations • Strengthening national greenhouse gas inventories • Improving independent estimates of fossil-fuel CO2 emissions • Improving independent estimates of fluxes from land-use sources and sinks

21. Improving Independent Estimates of Fossil-Fuel CO2 Emissions • Deploy a CO2-sensing satellite • Establish new atmospheric sampling stations (ground, ocean surface, aircraft) in strategic locations • Measure 14C in the CO2 samples already being collected

22. Recommendation NASA should build and launch a replacement for the Orbiting Carbon Observatory (OCO) • Most fossil-fuel CO2 emissions emanate from large local sources • OCO’s high precision and small sampling area could detect these signals and attribute them to the emitting country • Demonstrate the capability for monitoring CO2 from space for a climate treaty • Improve lifetime and coverage in future designs

23. Comparison of Satellite Capabilities 3 m s-1 4 Mt CO2 yr-1 CO2 signal would be detectable by OCO, but not by GOSAT (best available satellite) Example: 500 MW coal power plant

24. Recommendation Extend the international atmospheric sampling network: (1) to research the atmospheric “domes” of greenhouse gases over a representative sample of large local emitters, such as cities and power plants • Existing stations are located away from cities and power plants to study natural sources and sinks • New measurements at locations radiating from the center of selected large emitters would: • Document shifts in fuel sources in urban areas • Provide data to calibrate satellite measurements • Demonstrate a ground and aircraft monitoring capability

25. Recommendation Extend the international atmospheric sampling network: (2) to fill in underrepresented regions globally, thereby improving national sampling of regional greenhouse gas emissions. • Stations are capable of accurately detecting widespread, unconcentrated sources • New stations in high-emitting countries would improve tracer-transport modeling → improve independent verification of emissions • More frequent vertical profiles would constrain atmospheric transport → improve comparisons with satellite CO2 measurements

26. Recommendation Extend the capability of the CO2 sampling network to measure atmospheric 14C • Natural emissions of CO2 fluctuate and can be as large as fossil-fuel sources • CO2 from fossil-fuel and non-fossil-fuel sources can be differentiated using radiocarbon (14C) measurements • Modern organic material contains 14C from cosmic rays and bomb tests, but the 14C in fossil fuels has decayed away • Measurements could be made in CO2 samples that are already being collected at low cost

27. Problems with Tracer Transport Method • Transport Error • Large and incompletely understood background fluctuations of natural emissions. • Current sampling grid avoids urban areas and large industrial sources which generate most emissions. • Current sampling grid is too sparse.

28. Accuracy of Fossil-fuel CO2 Emissions Estimates

29. Categories of Recommendations • Strengthening national greenhouse gas inventories • Improving the ability to independently estimate fossil-fuel CO2 emissions • Improving independent estimates of fluxes from land-use sources and sinks

30. Improving Independent Estimates of Land-Use Emissions and Sinks • Produce global maps of land-use and land cover change • Design a research program to improve methods for estimating AFOLU emissions

31. Recommendation Establish a standing group to produce a global map of land-use and land cover change at least every 2 years. This will require a commitment to maintaining the continuous availability, in the public domain, of Landsat (or an equivalent satellite) and high-resolution satellite imagery. • Frequent mapping necessary to detect important changes (e.g., forest clearing or planting) • Provide an independent check on dominant sources of AFOLU CO2 emissions • Enable more accurate land-use emissions reporting from developing countries

32. Global maps Based on Landsat Publicly available, medium resolution Supplemented with targeted high-resolution imagery to monitor logging, forest degradation, and some agricultural practices (e.g., rice cultivation) NASA Earth Observatory

33. Recommendation An interagency group, with broad participation from the research community, should design a research program to improve and, where appropriate, implement methods for estimating agriculture, forestry, and other land-use emissions of CO2, N2O, and CH4 • Research to make more accurate estimates of AFOLU emissions • Emission factors: CO2 from deforestation and forest degradation, CH4 from rice paddies and cattle, and N2O from fertilizer application • Natural cycles of CO2, CH4, and N2O • Supporting observations, including flux measurements and ecosystem inventories (annual measurements of major carbon pools) • Improved methods could become part of UNFCCC reporting

34. Accuracy of AFOLU CO2 Emissions Estimates

35. Implications for Climate Agreements Implementing the recommendations would • Establish rigorous annual inventories for all countries as the core of a greenhouse gas monitoring system • Enable independent checks (<10% accuracy) on fossil-fuel combustion and deforestation, which are responsible for three-fourths of UNFCCC greenhouse gas emissions • Improve monitoring and verification of all greenhouse gases through targeted research

36. Simplifying the Monitoring and Verification Problem 90% of global emissions are from energy and AFOLU (agriculture, forestry, and other land use) → obvious focus for monitoring and verification